A humanized chemogenetic system inhibits murine pain-related behavior and hyperactivity in human sensory neurons

Hyperexcitability in sensory neurons is known to underlie many of the maladaptive changes associated with persistent pain. Chemogenetics has shown promise as a means to suppress such excitability, yet chemogenetic approaches suitable for human applications are needed. PSAM4-GlyR is a modular system based on the human α7 nicotinic acetylcholine and glycine receptors, which responds to inert chemical ligands and the clinically approved drug varenicline. Here, we demonstrated the efficacy of this channel in silencing both mouse and human sensory neurons by the activation of large shunting conductances after agonist administration. Virally mediated expression of PSAM4-GlyR in mouse sensory neurons produced behavioral hyposensitivity upon agonist administration, which was recovered upon agonist washout. Stable expression of the channel led to similar reversible suppression of pain-related behavior even after 10 months of viral delivery. Mechanical and spontaneous pain readouts were also ameliorated by PSAM4-GlyR activation in acute and joint pain inflammation mouse models. Furthermore, suppression of mechanical hypersensitivity generated by a spared nerve injury model of neuropathic pain was also observed upon activation of the channel. Effective silencing of behavioral hypersensitivity was reproduced in a human model of hyperexcitability and clinical pain: PSAM4-GlyR activation decreased the excitability of human-induced pluripotent stem cell-derived sensory neurons and spontaneous activity due to a gain-of-function NaV1.7 mutation causing inherited erythromelalgia. Our results demonstrate the contribution of sensory neuron hyperexcitability to neuropathic pain and the translational potential of an effective, stable, and reversible humanized chemogenetic system for the treatment of pain.

An iPSC model of hereditary sensory neuropathy-1 reveals L-serine-responsive deficits in neuronal ganglioside composition and axoglial interactions

Hereditary sensory neuropathy type 1 (HSN1) is caused by mutations in the SPTLC1 or SPTLC2 sub-units of the enzyme serine palmitoyltransferase, resulting in the production of toxic 1-deoxysphingolipid bases (DSBs). We used induced pluripotent stem cells (iPSCs) from patients with HSN1 to determine whether endogenous DSBs are neurotoxic, patho-mechanisms of toxicity and response to therapy. HSN1 iPSC-derived sensory neurons (iPSCdSNs) endogenously produce neurotoxic DSBs. Complex gangliosides, which are essential for membrane micro-domains and signaling, are reduced, and neurotrophin signaling is impaired, resulting in reduced neurite outgrowth. In HSN1 myelinating cocultures, we find a major disruption of nodal complex proteins after 8 weeks, which leads to complete myelin breakdown after 6 months. HSN1 iPSC models have, therefore, revealed that SPTLC1 mutation alters lipid metabolism, impairs the formation of complex gangliosides, and reduces axon and myelin stability. Many of these changes are prevented by l-serine supplementation, supporting its use as a rational therapy.

Establishing Myelinating Cocultures Using Human iPSC-Derived Sensory Neurons to Investigate Axonal Degeneration and Demyelination

Complex signaling between Schwann cells and axons are vital for peripheral neuron development, myelination, and repair. The interaction between these two cell types can be modeled in vitro by coculturing rodent Schwann cells and neurons together. These have in the past been used with great success to help unravel the bidirectional signaling mechanisms that lead to Schwann cell proliferation and myelination. To provide more translatable potential, we have developed myelinating cocultures using human, induced pluripotent stem cell (iPSC)-derived neurons. Under the right conditions, the human neurons are efficiently myelinated by rat Schwann cells, demonstrating successful cross-species signaling. This chapter describes all the necessary steps to generate these myelinating cocultures and methods to investigate and quantify various aspects of myelination. The myelinating cocultures can be maintained in excellent health for over 1 year, facilitating their use to study developmental or chronic disease processes. With this in mind, we have used the cocultures to model a sensory neuropathy which displays clinically with both axonal and demyelinating features. In the cocultures, we found evidence of extensive axonal degeneration and demyelination demonstrated by axonal swelling and fragmentation, and myelin disintegration. The myelinating cocultures can therefore be used to study complex, human disease processes that result in both axonal and myelin-associated degenerative processes.

Molecular and cellular correlates of human nerve regeneration: ADCYAP1/PACAP enhance nerve outgrowth

We only have a rudimentary understanding of the molecular and cellular determinants of nerve regeneration and neuropathic pain in humans. This cohort study uses the most common entrapment neuropathy (carpal tunnel syndrome) as a human model system to prospectively evaluate the cellular and molecular correlates of neural regeneration and its relationship with clinical recovery. In 60 patients undergoing carpal tunnel surgery [36 female, mean age 62.5 (standard deviation 12.2) years], we used quantitative sensory testing and nerve conduction studies to evaluate the function of large and small fibres before and 6 months after surgery. Clinical recovery was assessed with the global rating of change scale and Boston Carpal Tunnel Questionnaire. Twenty healthy participants provided normative data [14 female, mean age 58.0 (standard deviation 12.9) years]. At 6 months post-surgery, we noted significant recovery of median nerve neurophysiological parameters (P < 0.0001) and improvements in quantitative sensory testing measures of both small and large nerve fibre function (P < 0.002). Serial biopsies revealed a partial recovery of intraepidermal nerve fibre density [fibres/mm epidermis pre: 4.20 (2.83), post: 5.35 (3.34), P = 0.001], whose extent correlated with symptom improvement (r = 0.389, P = 0.001). In myelinated afferents, nodal length increased postoperatively [pre: 2.03 (0.82), post: 3.03 (1.23), P < 0.0001] suggesting that this is an adaptive phenomenon. Transcriptional profiling of the skin revealed 31 differentially expressed genes following decompression, with ADCYAP1 (encoding pituitary adenylate cyclase activating peptide, PACAP) being the most strongly upregulated (log2 fold-change 1.87, P = 0.0001) and its expression was associated with recovery of intraepidermal nerve fibres. We found that human induced pluripotent stem cell-derived sensory neurons expressed the receptor for PACAP and that this peptide could significantly enhance axon outgrowth in a dose-dependent manner in vitro [neurite length PACAP 1065.0 µm (285.5), vehicle 570.9 μm (181.8), P = 0.003]. In conclusion, carpal tunnel release is associated with significant cutaneous reinnervation, which correlates with the degree of functional improvement and is associated with a transcriptional programme relating to morphogenesis and inflammatory processes. The most highly dysregulated gene ADCYAP1 (encoding PACAP) was associated with reinnervation and, given that this peptide signals through G-protein coupled receptors, this signalling pathway provides an interesting therapeutic target for human sensory nerve regeneration.

Comparison of double inversion recovery magnetic resonance imaging (DIR-MRI) and dynamic contrast enhanced magnetic resonance imaging (DCE-MRI) in detection of prostate cancer: A pilot study

INTRODUCTION

DCE-MRI is established for detecting prostate cancer (PCa). However, it requires a gadolinium contrast agent, with potential risks for patients. The application of DIR-MRI is simple and may allow cancer detection without the use of an intravenous contrast agent by differentially nullifying signal from normal and abnormal prostate tissue, creating contrast between the cancer and background normal prostate. In this pilot study we gathered data from DIR-MRI and DCE-MRI of the prostate for an equivalence trial. We also looked at how the DIR-MRI appearance varies with the aggressiveness of PCa.

METHOD

DIR-MRI and DCE-MRI were acquired. The images were assessed by an experienced Consultant Radiologist and a novice reporter (Radiographer). The potential PCa lesions were quantified using a lesion to normal ratio (LNR). Radiological pathological correlation was made to identify the MRI lesions that represented significant PCa. A Wilcoxon sign rank was used to compare DCE-LNR and DIR-LNR for PCa containing lesions. Pearson's correlation was used to look at the relationship between DIR-LNR and PCa grade group (aggressiveness).

RESULTS

DCE-LNR and DIR-LNR were found to be significantly different (Z = -5.910, p < 0.001). However, a significant correlation was found between PCa grade group and DIR-LNR.

CONCLUSION

DIR and DCE sequences are not equivalent and significant cancer is more conspicuous on the DCE sequence. However, DIR-LNR does correlate with PCa aggressiveness.

IMPLICATIONS FOR PRACTICE

With the correlation of PCa grade group with DIR-LNR this may be a useful sequence in evaluation of the prostate; stratifying the risk of there being clinically significant PCa before biopsy is performed. Furthermore, given that DIR-LNR appears to predict PCa aggressiveness DIR might be used as part of a multiparametric MRI protocol designed to avoid biopsy.

Antidepressant treatment among social workers, human service professionals, and non-human service professionals: A multi-cohort study in Finland, Sweden and Denmark

BACKGROUND

Social workers have an elevated risk for mental disorders, but little is known about their antidepressant treatment.

AIMS

To examine any and long-term antidepressant treatment among social workers in Finland, Sweden and Denmark.

METHODS

We linked records from drug prescription registers to three prospective cohorts: the Finnish Public Sector study, years 2006-2011, and nation-wide cohorts in Sweden and Denmark, years 2006-2014, including a total of 1.5 million employees in (1) social work, (2) other social and health care professions, (3) education and (4) office work. We used Cox proportional hazards models to estimate hazard ratios for any and long-term (>6 months) antidepressant treatment among social workers compared to the three reference occupational groups and carried out meta-analyses.

RESULTS

During follow-up, 25% of social workers had any prescriptions for antidepressants (19-24% reference occupations) and 20% for long-term treatment (14-19% reference occupations). The pooled effects for any and long-term treatment showed that probabilities were 10% higher in social workers compared to other health and social care professionals and 30% higher compared to education and non-human service professionals. Probabilities for any treatment in the three countries were relatively similar, but for long-term treatment social workers in Finland had a greater risk compared with other human service professions.

LIMITATIONS

There were differences between the cohorts in the availability of data. Specific diagnoses for the antidepressant treatment were not known neither adherence to treatment.

CONCLUSION

Social workers have a higher risk for any and long-term antidepressant treatment than other human and non-human service professionals.

The Role of Voltage-Gated Sodium Channels in Pain Signaling

Acute pain signaling has a key protective role and is highly evolutionarily conserved. Chronic pain, however, is maladaptive, occurring as a consequence of injury and disease, and is associated with sensitization of the somatosensory nervous system. Primary sensory neurons are involved in both of these processes, and the recent advances in understanding sensory transduction and human genetics are the focus of this review. Voltage-gated sodium channels (VGSCs) are important determinants of sensory neuron excitability: they are essential for the initial transduction of sensory stimuli, the electrogenesis of the action potential, and neurotransmitter release from sensory neuron terminals. Nav1.1, Nav1.6, Nav1.7, Nav1.8, and Nav1.9 are all expressed by adult sensory neurons. The biophysical characteristics of these channels, as well as their unique expression patterns within subtypes of sensory neurons, define their functional role in pain signaling. Changes in the expression of VGSCs, as well as posttranslational modifications, contribute to the sensitization of sensory neurons in chronic pain states. Furthermore, gene variants in Nav1.7, Nav1.8, and Nav1.9 have now been linked to human Mendelian pain disorders and more recently to common pain disorders such as small-fiber neuropathy. Chronic pain affects one in five of the general population. Given the poor efficacy of current analgesics, the selective expression of particular VGSCs in sensory neurons makes these attractive targets for drug discovery. The increasing availability of gene sequencing, combined with structural modeling and electrophysiological analysis of gene variants, also provides the opportunity to better target existing therapies in a personalized manner.

Defining the Functional Role of NaV1.7 in Human Nociception

Loss-of-function mutations in NaV1.7 cause congenital insensitivity to pain (CIP); this voltage-gated sodium channel is therefore a key target for analgesic drug development. Utilizing a multi-modal approach, we investigated how NaV1.7 mutations lead to human pain insensitivity. Skin biopsy and microneurography revealed an absence of C-fiber nociceptors in CIP patients, reflected in a reduced cortical response to capsaicin on fMRI. Epitope tagging of endogenous NaV1.7 revealed the channel to be localized at the soma membrane, axon, axon terminals, and the nodes of Ranvier of induced pluripotent stem cell (iPSC) nociceptors. CIP patient-derived iPSC nociceptors exhibited an inability to properly respond to depolarizing stimuli, demonstrating that NaV1.7 is a key regulator of excitability. Using this iPSC nociceptor platform, we found that some NaV1.7 blockers undergoing clinical trials lack specificity. CIP, therefore, arises due to a profound loss of functional nociceptors, which is more pronounced than that reported in rodent models, or likely achievable following acute pharmacological blockade. VIDEO ABSTRACT.

Comprehensive analysis of long noncoding RNA expression in dorsal root ganglion reveals cell-type specificity and dysregulation after nerve injury

Dorsal root ganglion (DRG) neurons provide connectivity between peripheral tissues and the spinal cord. Transcriptional plasticity within DRG sensory neurons after peripheral nerve injury contributes to nerve repair but also leads to maladaptive plasticity, including the development of neuropathic pain. This study presents tissue and neuron-specific expression profiling of both known and novel long noncoding RNAs (LncRNAs) in the rodent DRG after nerve injury. We have identified a large number of novel LncRNAs expressed within the rodent DRG, a minority of which were syntenically conserved between the mouse, rat, and human, and including, both intergenic and antisense LncRNAs. We have also identified neuron type-specific LncRNAs in the mouse DRG and LncRNAs that are expressed in human IPS cell-derived sensory neurons. We show significant plasticity in LncRNA expression after nerve injury, which in mice is strain and gender dependent. This resource is publicly available and will aid future studies of DRG neuron identity and the transcriptional landscape in both the naive and injured DRG. We present our work regarding novel antisense and intergenic LncRNAs as an online searchable database, accessible from PainNetworks (http://www.painnetworks.org/). We have also integrated all annotated gene expression data in PainNetworks, so they can be examined in the context of their protein interactions.

Hereditary sensory neuropathy type 1-associated deoxysphingolipids cause neurotoxicity, acute calcium handling abnormalities and mitochondrial dysfunction in vitro

Hereditary sensory neuropathy type 1 (HSN-1) is a peripheral neuropathy most frequently caused by mutations in the SPTLC1 or SPTLC2 genes, which code for two subunits of the enzyme serine palmitoyltransferase (SPT). SPT catalyzes the first step of de novo sphingolipid synthesis. Mutations in SPT result in a change in enzyme substrate specificity, which causes the production of atypical deoxysphinganine and deoxymethylsphinganine, rather than the normal enzyme product, sphinganine. Levels of these abnormal compounds are elevated in blood of HSN-1 patients and this is thought to cause the peripheral motor and sensory nerve damage that is characteristic of the disease, by a largely unresolved mechanism. In this study, we show that exogenous application of these deoxysphingoid bases causes dose- and time-dependent neurotoxicity in primary mammalian neurons, as determined by analysis of cell survival and neurite length. Acutely, deoxysphingoid base neurotoxicity manifests in abnormal Ca2+ handling by the endoplasmic reticulum (ER) and mitochondria as well as dysregulation of cell membrane store-operated Ca2+ channels. The changes in intracellular Ca2+ handling are accompanied by an early loss of mitochondrial membrane potential in deoxysphingoid base-treated motor and sensory neurons. Thus, these results suggest that exogenous deoxysphingoid base application causes neuronal mitochondrial dysfunction and Ca2+ handling deficits, which may play a critical role in the pathogenesis of HSN-1.

Using an engineered glutamate-gated chloride channel to silence sensory neurons and treat neuropathic pain at the source

See Basbaum (doi:10.1093/brain/awx227) for a scientific commentary on this article. Peripheral neuropathic pain arises as a consequence of injury to sensory neurons; the development of ectopic activity in these neurons is thought to be critical for the induction and maintenance of such pain. Local anaesthetics and anti-epileptic drugs can suppress hyperexcitability; however, these drugs are complicated by unwanted effects on motor, central nervous system and cardiac function, and alternative more selective treatments to suppress hyperexcitability are therefore required. Here we show that a glutamate-gated chloride channel modified to be activated by low doses of ivermectin (but not glutamate) is highly effective in silencing sensory neurons and reversing neuropathic pain-related hypersensitivity. Activation of the glutamate-gated chloride channel expressed in either rodent or human induced pluripotent stem cell-derived sensory neurons in vitro potently inhibited their response to both electrical and algogenic stimuli. We have shown that silencing is achieved both at nerve terminals and the soma and is independent of membrane hyperpolarization and instead likely mediated by lowering of the membrane resistance. Using intrathecal adeno-associated virus serotype 9-based delivery, the glutamate-gated chloride channel was successfully targeted to mouse sensory neurons in vivo, resulting in high level and long-lasting expression of the channel selectively in sensory neurons. This enabled reproducible and reversible modulation of thermal and mechanical pain thresholds in vivo; analgesia was observed for 3 days after a single systemic dose of ivermectin. We did not observe any motor or proprioceptive deficits and noted no reduction in cutaneous afferent innervation or upregulation of the injury marker ATF3 following prolonged glutamate-gated chloride channel expression. Established mechanical and cold pain-related hypersensitivity generated by the spared nerve injury model of neuropathic pain was reversed by ivermectin treatment. The efficacy of ivermectin in ameliorating behavioural hypersensitivity was mirrored at the cellular level by a cessation of ectopic activity in sensory neurons. These findings demonstrate the importance of aberrant afferent input in the maintenance of neuropathic pain and the potential for targeted chemogenetic silencing as a new treatment modality in neuropathic pain.

No support for Heincke's law in hagfish (Myxinidae): lack of an association between body size and the depth of species occurrence

This study tests for interspecific evidence of Heincke's law among hagfishes and advances the field of research on body size and depth of occurrence in fishes by including a phylogenetic correction and by examining depth in four ways: maximum depth, minimum depth, mean depth of recorded specimens and the average of maximum and minimum depths of occurrence. Results yield no evidence for Heincke's law in hagfishes, no phylogenetic signal for the depth at which species occur, but moderate to weak phylogenetic signal for body size, suggesting that phylogeny may play a role in determining body size in this group.

Informal caregiving as a risk factor for type 2 diabetes in individuals with favourable and unfavourable psychosocial work environments: A longitudinal multi-cohort study

AIM

To examine whether informal caregiving is associated with increased risk of type 2 diabetes (T2D), and whether job strain and social support at work modify the association.

METHODS

Individual participant's data were pooled from three cohort studies-the French GAZEL study, the Swedish Longitudinal Occupational Survey of Health (SLOSH) and the British Whitehall II study-a total of 21,243 study subjects. Informal caregiving was defined as unpaid care for a closely related person. Job strain was assessed using the demand-control model, and questions on co-worker and supervisor support were combined in a measure of social support at work. Incident T2D was ascertained using registry-based, clinically assessed and self-reported data.

RESULTS

A total of 1058 participants developed T2D during the up to 10 years of follow-up. Neither informal caregiving (OR: 1.09, 95% CI: 0.92-1.30) nor high job strain (OR: 1.04, 95% CI: 0.86-1.26) were associated with T2D risk, whereas low social support at work was a risk factor for T2D (OR: 1.18, 95% CI: 1.02-1.37). Also, informal caregivers who were also exposed to low social support at work were at higher risk of T2D (OR: 1.40, 95% CI: 1.08-1.82) compared with those who were not informal caregivers and had high social support at work (multiplicative test for interaction, P=0.04; additive test for interaction, synergy index=10).

CONCLUSION

Informal caregiving was not independently associated with T2D risk. However, low social support at work was a risk factor, and informal caregivers with low social support at work had even higher risks of T2D.

Co-cultures with stem cell-derived human sensory neurons reveal regulators of peripheral myelination

See Saporta and Shy (doi:10.1093/awx048) for a scientific commentary on this article.Effective bidirectional signalling between axons and Schwann cells is essential for both the development and maintenance of peripheral nerve function. We have established conditions by which human induced pluripotent stem cell-derived sensory neurons can be cultured with rat Schwann cells, and have produced for the first time long-term and stable myelinating co-cultures with human neurons. These cultures contain the specialized domains formed by axonal interaction with myelinating Schwann cells, such as clustered voltage-gated sodium channels at the node of Ranvier and Shaker-type potassium channel (Kv1.2) at the juxtaparanode. Expression of type III neuregulin-1 (TIIINRG1) in induced pluripotent stem cell-derived sensory neurons strongly enhances myelination, while conversely pharmacological blockade of the NRG1-ErbB pathway prevents myelination, providing direct evidence for the ability of this pathway to promote the myelination of human sensory axons. The β-secretase, BACE1 is a protease needed to generate active NRG1 from the full-length form. Due to the fact that it also cleaves amyloid precursor protein, BACE1 is a therapeutic target in Alzheimer's disease, however, consistent with its role in NRG1 processing we find that BACE1 inhibition significantly impairs myelination in our co-culture system. In order to exploit co-cultures to address other clinically relevant problems, they were exposed to anti-disialosyl ganglioside antibodies, including those derived from a patient with a sensory predominant, inflammatory neuropathy with mixed axonal and demyelinating electrophysiology. The co-cultures reveal that both mouse and human disialosyl antibodies target the nodal axolemma, induce acute axonal degeneration in the presence of complement, and impair myelination. The human, neuropathy-associated IgM antibody is also shown to induce complement-independent demyelination. Myelinating co-cultures using human induced pluripotent stem cell-derived sensory neurons thus provide insights into the cellular and molecular specialization of axoglial signalling, how pharmacological agents may promote or impede such signalling and the pathogenic effects of ganglioside antibodies.awx012media15372351982001.

Pain expectations in neuropathic pain: Is it best to be optimistic?

BACKGROUND

Pain expectancy may be an important variable that has been found to influence the effectiveness of treatments for pain. Much of the literature supports a self-fulfilment perspective where expectations for pain relief predict the actual pain experienced. However, in conditions such as neuropathic pain (NeP) where pain relief is difficult to attain, expectations for pain relief could be unrealistic. The objective of this study was to investigate the relationship between realistic/unrealistic expectations and 6-month, post-treatment outcomes.

METHODS

We performed a retrospective analysis of a large cohort of patients with NeP (n = 789) attending tertiary care centres to determine the association between unrealistic (both positive and negative) and realistic expectations with outcomes after multidisciplinary treatment. An expectation variable with three categories was calculated: realistic expectations were those whose expected reduction in pain was similar to the observed mean group reduction in pain, while optimistic and pessimistic expectations were those who over- or under-estimated the expected response to treatment, respectively. The association between baseline realistic/unrealistic expectations and 6-month pain-related disability, catastrophizing and psychological distress was assessed.

RESULTS

Univariable analyses suggested that realistic expectations were associated with lower levels of disability, catastrophizing and psychological distress, compared to unrealistic expectations. However, after adjustment for baseline symptom severity, multivariable analysis revealed that patients with optimistic expectations had lower levels of disability, than those with realistic expectations. Those with pessimistic expectations had higher levels of catastrophizing and psychological distress at follow-up.

CONCLUSIONS

These findings are largely congruent with the self-fulfilment perspective to expectations.

SIGNIFICANCE

This study defined realistic pain expectations with patient data. Examining the relationship between expectations between pain and disability in a large cohort of patients with neuropathic pain.

Pharmacological management of chronic neuropathic pain: revised consensus statement from the Canadian Pain Society

BACKGROUND

Neuropathic pain (NeP), redefined as pain caused by a lesion or a disease of the somatosensory system, is a disabling condition that affects approximately two million Canadians.

OBJECTIVE

To review the randomized controlled trials (RCTs) and systematic reviews related to the pharmacological management of NeP to develop a revised evidence-based consensus statement on its management.

METHODS

RCTs, systematic reviews and existing guidelines on the pharmacological management of NeP were evaluated at a consensus meeting in May 2012 and updated until September 2013. Medications were recommended in the consensus statement if their analgesic efficacy was supported by at least one methodologically sound RCT (class I or class II) showing significant benefit relative to placebo or another relevant control group. Recommendations for treatment were based on the degree of evidence of analgesic efficacy, safety and ease of use.

RESULTS

Analgesic agents recommended for first-line treatments are gabapentinoids (gabapentin and pregabalin), tricyclic antidepressants and serotonin noradrenaline reuptake inhibitors. Tramadol and controlled-release opioid analgesics are recommended as second-line treatments for moderate to severe pain. Cannabinoids are now recommended as third-line treatments. Recommended fourth-line treatments include methadone, anticonvulsants with lesser evidence of efficacy (eg, lamotrigine, lacosamide), tapentadol and botulinum toxin. There is support for some analgesic combinations in selected NeP conditions.

CONCLUSIONS

These guidelines provide an updated, stepwise approach to the pharmacological management of NeP. Treatment should be individualized for each patient based on efficacy, side-effect profile and drug accessibility, including cost. Additional studies are required to examine head-to-head comparisons among analgesics, combinations of analgesics, long-term outcomes and treatment of pediatric, geriatric and central NeP.

Guidelines for the use of cannabinoid compounds in chronic pain

OBJECTIVE

To provide clinicians with guidelines for the use of cannabinoid compounds in the treatment of chronic pain.

METHODS

Publications indexed from 1990 to 2005 in the National Library of Medicine Index Medicus were searched through PubMed. A consensus concerning these guidelines was achieved by the authors through review and discussion.

RESULTS

There are few clinical trials, case reports or case series concerning the use of cannabinoid compounds in the treatment of chronic pain. There are no randomized clinical trials examining the use of herbal cannabis in the treatment of chronic pain.

CONCLUSIONS

A practical approach to the treatment of chronic pain with cannabinoid compounds is presented. Specific suggestions about the off-label dosing of nabilone (Cesamet, Valeant Canada limitee/Limited) and dronabinol (Marinol, Solvay Pharma Inc, Canada) in the treatment of chronic pain are provided.

Deficiency of ALADIN impairs redox homeostasis in human adrenal cells and inhibits steroidogenesis

Triple A syndrome is a rare, autosomal recessive cause of adrenal failure. Additional features include alacrima, achalasia of the esophageal cardia, and progressive neurodegenerative disease. The AAAS gene product is the nuclear pore complex protein alacrima-achalasia-adrenal insufficiency neurological disorder (ALADIN), of unknown function. Triple A syndrome patient dermal fibroblasts appear to be more sensitive to oxidative stress than wild-type fibroblasts. To provide an adrenal and neuronal-specific disease model, we established AAAS-gene knockdown in H295R human adrenocortical tumor cells and SH-SY5Y human neuroblastoma cells by lentiviral short hairpin RNA transduction. AAAS-knockdown significantly reduced cell viability in H295R cells. This effect was exacerbated by hydrogen peroxide treatment and improved by application of the antioxidant N-acetylcysteine. An imbalance in redox homeostasis after AAAS knockdown was further suggested in the H295R cells by a decrease in the ratio of reduced to oxidized glutathione. AAAS-knockdown SH-SY5Y cells were also hypersensitive to oxidative stress and responded to antioxidant treatment. A further impact on function was observed in the AAAS-knockdown H295R cells with reduced expression of key components of the steroidogenic pathway, including steroidogenic acute regulatory and P450c11β protein expression. Importantly a significant reduction in cortisol production was demonstrated with AAAS knockdown, which was partially reversed with N-acetylcysteine treatment.

CONCLUSION

Our in vitro data in AAAS-knockdown adrenal and neuronal cells not only corroborates previous studies implicating oxidative stress in this disorder but also provides further insights into the pathogenic mechanisms in triple A syndrome.

Psychosocial risk factors, pre-motor symptoms and first-time hospitalization with Parkinson's disease: a prospective cohort study

BACKGROUND AND PURPOSE

Experimental studies support a link between stress and development of parkinsonian symptoms, but prospective population studies are lacking. The aim of the current study is to determine the effects of several psychosocial factors on the risk of Parkinson's disease (PD), as well as to identify potential pre-motor symptoms for PD in a large prospective cohort study.

METHODS

In 1991-1993, a total of 9955 women and men free of PD from the Copenhagen City Heart Study were asked about major life events, economic hardship, social network, impaired sleep and vital exhaustion. The participants were followed for first-time hospitalization with PD in nationwide registers until 2011.

RESULTS

Vital exhaustion was associated with a higher risk of PD hospitalization in an exposure-dependent manner (P(trend) = 0.001), with high vs. low vital exhaustion being associated with a hazard ratio of 2.50 [95% confidence interval (CI): 1.28-4.89]. A slightly higher risk of PD hospitalization (hazard ratio = 1.49; 95% CI: 0.87-2.56) was suggested in participants with impaired sleep at baseline. No more than weak associations were observed for economic hardship, major life events or inadequate social network in the current study.

CONCLUSIONS

Overall, the hypothesis that psychosocial risk factors affect the risk of PD is not supported. The results, however, suggest that vital exhaustion may be a pre-motor marker of the neurodegenerative process eventually leading to motor symptoms and clinical PD. Vital exhaustion may be useful for screening aimed at early detection and when considering disease-modifying therapies in people at high risk of clinical PD.

Prolonged swing phase rectus femoris activity is not associated with stiff-knee gait in children with cerebral palsy: a retrospective study of 407 limbs

Prolonged swing phase rectus femoris (RF) activity has been implicated as a cause of stiff-knee gait (SKG) in children with cerebral palsy (CP) and continues to be cited as an indicator for RF intervention. The purpose of this study was to determine what, if any, association exists between abnormal RF activity during preswing, initial swing and/or midswing and SKG in children with CP. This retrospective analysis involved three examiners independently reviewing sagittal plane knee kinematic and RF surface electromyographic (EMG) data from 407 affected limbs of 234 pediatric patients with CP. Five kinematic parameters were rated by each examiner as normal or pathologic: peak knee flexion, knee range of motion during initial swing, total knee range of motion, peak knee flexion timing, and rate of knee flexion. These ratings were used to classify each limb into one of three groups: SKG, Borderline SKG, or Non-SKG. From a representative EMG tracing, RF activity was examined during: the first half of preswing, the latter 2/3 of initial swing, and midswing. Chi-squared tests were used to determine if significant associations existed between SKG and RF activation during these three subphases. There was no association between SKG and prolonged RF activity during the latter 2/3 of initial swing or during midswing. However, a significant relationship between SKG and RF activity during the first half of preswing was found (p<0.001). Neither prolonged RF activity during initial swing, nor the presence of RF activity during midswing, were associated with SKG, thus refuting these commonly held associations.

Thermodynamic consistency in variable-level coarse graining of polymeric liquids

Numerically optimized reduced descriptions of macromolecular liquids often present thermodynamic inconsistency with atomistic level descriptions even if the total correlation function, i.e. the structure, appears to be in agreement. An analytical expression for the effective potential between a pair of coarse-grained units is derived starting from the first-principles Ornstein-Zernike equation, for a polymer liquid where each chain is represented as a collection of interpenetrating blobs, with a variable number of blobs, n(b), of size N(b). The potential is characterized by a long tail, slowly decaying with characteristic scaling exponent of N(b)(1/4). This general result applies to any coarse-grained model of polymer melts with units larger than the persistence length, highlighting the importance of the long, repulsive, potential tail for the model to correctly predict both structural and thermodynamic properties of the macromolecular liquid.

Ontogenetic scaling of the morphology and biomechanics of the feeding apparatus in the Pacific hagfish Eptatretus stoutii

The form and function of the support skeleton, musculature and teeth were examined in an ontogenetic series of Pacific hagfish Eptatretus stoutii spanning about a six-fold range in total length (L(T)). Tooth area, feeding apparatus length, basal plate size, theoretical dental plate retractile force, penetration force and applied tooth stress were measured relative to body size. Morphological variables (e.g. tooth area and basal plate size) scaled with positive allometry and functional variables (e.g. retractile force and applied tooth stress) scaled isometrically with L(T). These results suggest that juveniles do not undergo ontogenetic dietary changes and consume functionally equivalent prey to adults, although adults can grasp proportionally larger portions of food. Low tooth stress in juveniles and adults imposes mechanical constraints to puncturing and tearing, which are circumvented by a preference for softer prey tissue or the inclusion of knotting behaviours for reducing tougher prey.

Laparoscopic resection of advanced colorectal cancer

Background

Palliative resection of the primary tumour in asymptomatic patients with stage IV colorectal cancer is associated with improved survival and fewer complications. Laparoscopic surgery is widely employed in the curative treatment of colorectal cancer, but its value in advanced colorectal cancer remains unclear.

Methods

All patients who underwent laparoscopic resection of primary colorectal cancer in this unit between June 1991 and Jan 2010 were entered into a prospective computerized database. Outcomes for patients with laparoscopic resection of stage IV colorectal cancer were compared with those of patients who had laparoscopic surgery for stage I disease.

Results

Some 185 patients with stage IV colorectal cancer who underwent laparoscopic resection were compared with 310 patients who had stage I colorectal cancer. Some 94·1 and 98·4 per cent of operations respectively were completed laparoscopically. Hospital stay was slightly longer in the group with stage IV disease (mean 6·2 versus 5·3 days; P = 0·091). The 30-day mortality rate was 2·7 per cent in patients with stage IV disease and 0·6 per cent in those with stage I tumours (P = 0·061). There was no difference in complications. One-year survival rates were 77·8 and 99·0 per cent respectively (P &lt; 0·001).

Conclusion

Short-term outcomes after laparoscopic surgery for stage IV colorectal cancer in selected patients are equivalent to those for stage I cancers.

The replication fork's five degrees of freedom, their failure and genome rearrangements

Genome rearrangements are important in pathology and evolution. The thesis of this review is that the genome is in peril when replication forks stall, and stalled forks are normally rescued by error-free mechanisms. Failure of error-free mechanisms results in large-scale chromosome changes called gross chromosomal rearrangements, GCRs, by the aficionados. In this review we discuss five error-free mechanisms a replication fork may use to overcome blockage, mechanisms that are still poorly understood. We then speculate on how genome rearrangements may occur when such mechanisms fail. Replication fork recovery failure may be an important feature of the oncogenic process. (Feedback to the authors on topics discussed herein is welcome.).

Traumatic extrathoracic lung herniation

We report a case of traumatic extrathoracic lung herniation. This is a rare injury that is potentially life threatening. The imaging features, associated injuries and complications are discussed to facilitate rapid recognition for best patient outcome. Uniquely, we demonstrate the injury with a three-dimensional reconstructed minimum intensity projection.

Pharmacological management of chronic neuropathic pain - consensus statement and guidelines from the Canadian Pain Society

Neuropathic pain (NeP), generated by disorders of the peripheral and central nervous system, can be particularly severe and disabling. Prevalence estimates indicate that 2% to 3% of the population in the developed world suffer from NeP, which suggests that up to one million Canadians have this disabling condition. Evidence-based guidelines for the pharmacological management of NeP are therefore urgently needed. Randomized, controlled trials, systematic reviews and existing guidelines focusing on the pharmacological management of NeP were evaluated at a consensus meeting. Medications are recommended in the guidelines if their analgesic efficacy was supported by at least one methodologically sound, randomized, controlled trial showing significant benefit relative to placebo or another relevant control group. Recommendations for treatment are based on degree of evidence of analgesic efficacy, safety, ease of use and cost-effectiveness. Analgesic agents recommended for first-line treatments are certain antidepressants (tricyclics) and anticonvulsants (gabapentin and pregabalin). Second-line treatments recommended are serotonin noradrenaline reuptake inhibitors and topical lidocaine. Tramadol and controlled-release opioid analgesics are recommended as third-line treatments for moderate to severe pain. Recommended fourth-line treatments include cannabinoids, methadone and anticonvulsants with lesser evidence of efficacy, such as lamotrigine, topiramate and valproic acid. Treatment must be individualized for each patient based on efficacy, side-effect profile and drug accessibility, including cost. Further studies are required to examine head-to-head comparisons among analgesics, combinations of analgesics, long-term outcomes, and treatment of pediatric and central NeP.